Yet another n00b setup question
I'm about 200 pounds, and I commute 20 miles to work each way. There are some hills, but they're not too bad. I can take the hills under my own power, it's just slow. I want to speed up my commute and make the uphill sections faster and easier.
I am considering adding a Roadrunner 4820 to my bike, powered by a Yesu LiFePo4 48V 10Ah battery. From what I read, this battery should take me 10-15 miles without any pedaling at all, and I like pedaling. I am fine pedaling the whole way, I just want to speed things up.
From what I read, this setup should get close to 25MPH... I don't think the gearing on my current bike will let me pedal at that speed. So I'm concerned that if I can't pedal assist for most of the distance, the battery will not last for the full commute. Has anyone tried getting a bigger chain ring so they can pedal assist at higher speeds? Would it make sense to do that?
My other concern is that the motor might add some resistance when the battery runs out, or if I choose to turn the throttle off for long flat sections. Will putting this motor on my bike make it a lot harder to ride when the battery is out of juice? (not counting the extra 25 pounds or so)
Should I consider the 20Ah battery? That seems like it might be overkill for me, and they're not cheap!
Yes, a bigger chainring would help you peadal more, and there are lots of other tricks to extend range.
Yes you need the 20 ah to go 20 miles day in and day out. Some batteries will cut out on hills and such if less than 20 ah. If you use less than 80% of the capacity instead of 100% of it you will get more cycles out of the battery, and GREATLY reduce the risk of an overdischarge. This is really important with lithium. The BMS is supposed to prevent this, but it's like parachuting, it better work every time. I'd rather not ask the bms to take action by using less than 100% of the charge. I like a big fudge factor on things.
No you do not want to peadle the unenergized bike. There will be a slighltly noticeable drag from the motor, and a REALLY noticalble extra 50 pounds. Think of a bike with a rebar frame. Not fun unless you like a workout.
20 ah from yesa is expensive, but try ping, I heard he may be back in buisness, having a new way to ship. just email him, his website, pingbattery has the email address. Another newbie just found a good deal at Fox Battery. Those look comparable to the yesas and are pretty good price.
If you are going 20 miles to work every day, a 20 Ah battery is not overkill. You will use the bike more if you know you have enough power to make the trip even when you are sick, tired, or otherwise unable to pedal. For an added bonus, the higher amp-hour battery will last much longer.
As I understand these packs 1 - 20AH is the same as 2 - 10AH since each pack is made from the same cells. The 20AH just has twice as many cells as the 10AH. Hope this answers your question.
Grandpa Chas S.